Prop attachment

How do you get your props to stay on? I have had a working board for a while now, but the 3d printed props have either come off or broken. Just received a solas prop and will try that one. I know that won’t crack, but don’t want to lose another prop.
Currently I am just screwing them on the threaded shaft. Works if the prop is spinning the correct direction to tighten when it hits the water. The 3d printed ones crack after a few minutes. I think infill should be higher, but how high?

100% infill ?

A normal small prop has a pin at the rear and a bolt and washer on the front to squeeze it towards the pin

100% infill, 16/20mm pin (I use stainless steel 16mm 3mm thick, just drill the shaft close to the motor side of propeller, use a self locking nut, aka Nyloc. Do not overtighten the nut, it’s just a retainer, torque is transmitted by the pin.
Epoxying the 3d printed plastic improve the resistance a little